Oscillators or clock generators can be realized with various types of circuit technology. High accuracies can be achieved with quartz oscillators, but such quartz oscillators require an external component, namely the quartz, which increases the production cost of integrated circuits. In addition, appropriate quartz oscillators are usually only specified up to a maximum temperature of 125° C.
In another conventional manner of implementing an oscillator, two capacitors are alternately charged with a defined charge current up to a defined reference voltage. The charge voltage of the capacitor is compared with respective comparators, with the output signal of the comparator changing a state of a flipflop. This output state of the flipflop then ends the charging process of the one capacitor and starts the charging process of the other capacitor, until it too has reached the reference voltage. The output signal of the flipflop serves as the clock signal to be generated.
A frequency, or a period duration of the clock signal, results from the time duration of the charging process until the reference voltage is reached, wherein the switching time of the comparators when the reference potential is exceeded by the charge voltage also has to be taken into consideration.
The switching times of the comparators are typically strongly dependent on the temperature. If, in addition, the proportion of the comparator switching time in the period duration of the clock signal is high, this results in a temperature-dependence of the entire period duration, and thus of the oscillator frequency.